The silver shovel may seem pretty awful, but it's far from it.
When hitting the money rock for bells, it has 10% chance of giving you 2 times the amount of bells, or around 16,000 bells!
Here's how to get it:
Go to the city after 8 PM and go right. On some days, cones will be blocking the path into the tunnel, but on a random day, the cones will be pushed aside and light will come out. (Keep trying until this happens!)
Go inside, and there you will see Resetti in the Surveillance Center.
Talk to him, and don't leave. Just keep talking until he gives you the Silver Shovel, and then leave.
Congratulations, you now have the Silver Shovel!
Hope I helped.